1. Field of the Invention
The present invention relates to a method for manufacturing a divided waveplate filter for, for example, a stereoscopic image display unit.
2. Description of the Related Art
Various technologies for representing images three-dimensionally were tried in the past. Many display methods for three-dimensional images have been studied and put to practical use in many fields, such as, photography, movies, and television. The display methods of three-dimensional images are roughly separated into methods with and without eyeglasses. In both methods, images having binocular parallax are input into the right eye and the left eye of a viewer, and the viewer can see the images as a stereoscopic image.
Typical methods with eyeglasses include a so-called anaglyph method using red-blue glasses and a method using polarization eyeglasses. Unfortunately, color separation methods such as the anaglyph method have qualitative disadvantages, for example, difficulty in color expression and a deterioration of a visual field. The method using polarization eyeglasses generally requires two projectors; a method for stereoscopic display using a direct-view display unit is proposed in recent years.
FIG. 19 is a schematic view of a stereoscopic image display unit using polarization eyeglasses.
A stereoscopic image display unit 200 includes a liquid crystal panel unit 201 and a divided waveplate filter part 202 attached to the liquid crystal panel unit 201. In the liquid crystal panel unit 201, a pair of transparent support substrates 204 and 206 is disposed between a pair of polarizer 203 and 207. A pixellated liquid crystal part 205 including RGB pixels is disposed between the transparent support substrates. The divided waveplate filter part 202 is disposed on the surface of the liquid crystal panel unit 201. In the divided waveplate filter part 202, for example, divided waveplates 208 are disposed with gaps therebetween on a single side of the transparent support substrate 209. The divided waveplate filter part 202 is also called a micro-pol (μ-pol) or a micropolarizer.
In the stereoscopic image display unit 200 having such a structure, linear polarizations from even-numbered lines and odd-numbered lines of the display screen are converted to be orthogonal by rotating the linear polarizations emitted from the liquid crystal panel unit 201. Accordingly, one linear polarization from the liquid crystal panel unit 201 is emitted as is from the even-numbered lines, and one linear polarization from the liquid crystal panel is emitted from the odd-numbered lines to be orthogonal because of the function of the divided waveplates 208.
The respective eyes of the eyeglasses 210 let in orthogonal light from the display unit in the polarization direction thereof. When a viewer observes with the eyeglasses 210, light of the image for the right eye is incident on the right eye and light of the image for the left eye is incident on the left eye. Accordingly, the viewer can see a full-color stereoscopic image without flicker.
As described above, the stereoscopic image display unit 200 includes the liquid crystal panel unit 201 and divided waveplate filter part 202, thereby enabling the display of stereoscopic images. The viewer can see the stereoscopic images by wearing the polarization eyeglasses 210. In the liquid crystal panel unit 201, the pixellated liquid crystal part 205 is disposed between the pair of transparent support substrates 204 and 206, and is composed of a combination of red pixels (R), green pixels (G), and blue pixels (B). In the pixellated liquid crystal part 205, pixel portions composed of the three colors are arranged in a matrix.
The light passing through the polarizer 207 disposed at the viewer-side of the transparent support substrate 206 becomes linearly polarized. The linearly polarized light is then incident on the divided waveplate filter part 202. The divided waveplate filter part 202 includes a transparent support substrate 209 composed of, for example, glass, which functions as a frame. The strip-shaped divided waveplates 208 are disposed at the liquid crystal panel unit 201 side of the transparent support substrate 209. The divided waveplates 208 extend such that the longitudinal direction is the horizontal direction. The width of each strip is about the same as the pixel pitch of the pixellated liquid crystal part 205. The number of the divided waveplates 208 is half of the number of pixels in vertical direction of the pixellated liquid crystal part 205.
The strip-shaped divided waveplates 208 are disposed with gaps therebetween at the pixel pitch of the pixellated liquid crystal part 205. Accordingly, either a stereoscopic image for the right eye or a stereoscopic image for the left eye passes through the divided waveplates 208, thereby rotating the polarization direction by 90°. The other stereoscopic image, which does not pass through the divided waveplates 208, is emitted without rotating its polarization direction.
As described above, the polarization on the stereoscopic image is controlled in each line to have different polarization directions. After passing through the divided waveplates 208, two orthogonal linear polarizations are mixed. Accordingly, a viewer wearing the polarization eyeglasses 210 can see the stereoscopic image with both eyes by selectively receiving the stereoscopic image for the right eye and the stereoscopic image for the left eye.
In the stereoscopic image display unit 200 as described above, in order to satisfactorily appreciate the stereoscopic image without cross talk, the strip-shaped divided waveplates 208 are formed so as to accurately correspond to the pixel pitch. That is, the strip-shaped divided waveplates 208 are accurately arrayed to the stripe lines of the pixellated liquid crystal part 205.
Accordingly, there have been increasing demands for manufacturing the divided waveplates 208 with high precision. The following needs should be satisfied: The divided waveplates 208 having fine widths (100 μm to 200 μm) should be precisely manufactured. The divided waveplates 208 having a precise shape and uniform thickness should be disposed with gaps therebetween. The shape and width of the divided waveplates 208 should be uniform over the plane. Furthermore, the divided waveplates 208 having such precise and uniform shapes must be manufactured stably and with good reproducibility.
FIG. 20 is a schematic perspective view showing an example of a conventional manufacturing method of the divided waveplates 208. A grinder 20 is used for conventionally manufacturing the divided waveplates 208. The grinder 20 has a grinding stone having a small width. The grinder 20 is used for forming stripe shapes of a phase difference material layer 3, for example a phase difference film, disposed on the transparent support substrate (hereinafter referred to as glass substrate) 209. Specifically, the phase difference material layer 3 is scraped away every other line with the grinder 20, thereby forming removed portions 4 and divided waveplates 208.
Unfortunately, since the phase difference material layer 3 is composed of a resin, the grinding stone of the grinder 20 becomes clogged with the resin. Accordingly fine processing is difficult to achieve. Furthermore, resin softened by frictional heat limits the revolving speed of the grinder 20. In addition, grinders cannot be arranged in a row. Accordingly, mass production of the divided waveplates is difficult by the conventional method and a rapid solution to these problems is required.